Strange 944 Running/ No Start Issues....
02-07-2019, 06:42 AM
#46
Burning Brakes
great post jacob............. I can see that you have been extremely thorough in your testing and followed the Porsche Workshop Manual .I'm impressed ...Good work !
With all the work you have done and the parts replaced you have to wonder what on earth could still be wrong with the car but Springs post highlights potential faults that are often overlooked . How many owners possess a Noid light !? .
Ground or earthing points too are so often overlooked . owners think that they are such a mundane component that they couldn't possibly be the reason for a failure.
On the late 944 the ECU is located under the passenger carpet . Above the ECU alongside the fuse relay box there are 2x vital ground points for the ECU under the dash on the scuttle .
I cannot remember where the ECU and the fuse/relay box and ground points are on the early 944 but I believe that none of them are in the same place as the early cars
It is essential that you find these ground points and remove and clean them when you replace the wiring loom as a lot of the work that the ECU does is by grounding components using those specific ground points
Good luck with the rewire I shall monitor progress with interest
With all the work you have done and the parts replaced you have to wonder what on earth could still be wrong with the car but Springs post highlights potential faults that are often overlooked . How many owners possess a Noid light !? .
Ground or earthing points too are so often overlooked . owners think that they are such a mundane component that they couldn't possibly be the reason for a failure.
On the late 944 the ECU is located under the passenger carpet . Above the ECU alongside the fuse relay box there are 2x vital ground points for the ECU under the dash on the scuttle .
I cannot remember where the ECU and the fuse/relay box and ground points are on the early 944 but I believe that none of them are in the same place as the early cars
It is essential that you find these ground points and remove and clean them when you replace the wiring loom as a lot of the work that the ECU does is by grounding components using those specific ground points
Good luck with the rewire I shall monitor progress with interest
02-07-2019, 06:12 PM
#48
Drifting
Thanks to this forum (and Vitesse John), this year I learned the awesomeness of a simple (and cheap) 12v LED light for diagnosis. This can be had at any electronics supply.
So easy to see injector signals, coil signals, lots of signals. Everyone should have one in the car's armrest or glovebox. Quicker & easier than a voltmeter, noid light, etc
So easy to see injector signals, coil signals, lots of signals. Everyone should have one in the car's armrest or glovebox. Quicker & easier than a voltmeter, noid light, etc
02-20-2019, 02:16 PM
#49
GREAT NEWS
SHE STARTS
AND RUNS.....
for about 3 or four seconds Hahahahahahaha. Then dies.
But im confident the original flooding issue is resolved as the car starts every single time I jump it. No smoke or fuel smell.
Where do i I go from here?
When it dies it dies instantly.
02-20-2019, 02:38 PM
#50
Burning Brakes
have you done a search on this forum and the net for '944 starts and dies ' ??
Firstly are you using the DME relay or have you fitted a 3x wire bypass whilst you are testing ? If you are using the DME relay again then that would be my first port of call.
Stick the bypass in there so that everything is supplied with power constantly and try that
If it were me I would fit a fuel pressure gauge to the fuel rail so that I could monitor the fuel pressure all the time when starting and running the car. This will eliminate fuel pressure being the culpret
Either you are losing fuel air or ignition spark and knowing which would narrow down your search considerably.
Firstly are you using the DME relay or have you fitted a 3x wire bypass whilst you are testing ? If you are using the DME relay again then that would be my first port of call.
Stick the bypass in there so that everything is supplied with power constantly and try that
If it were me I would fit a fuel pressure gauge to the fuel rail so that I could monitor the fuel pressure all the time when starting and running the car. This will eliminate fuel pressure being the culpret
Either you are losing fuel air or ignition spark and knowing which would narrow down your search considerably.
02-20-2019, 02:44 PM
#51
I’ve been searching and I’ll keep doing so.
Ive got a fuel pressure gauge installed in the car and my fuel pressure is good.
Im leaning more towards vacuum at this point I’ll keep chasing that down.
Ive got a fuel pressure gauge installed in the car and my fuel pressure is good.
Im leaning more towards vacuum at this point I’ll keep chasing that down.
02-20-2019, 03:01 PM
#52
Burning Brakes
have you got the 3x wire bypass fitted whilst you are testing ?
I don't understand why there is a reluctance to do this . it immediately eliminates a lot of components .
Don't rule our your ignition switch having a bad connection or the base connector for the DME relay in the fuse relay box .
I don't understand why there is a reluctance to do this . it immediately eliminates a lot of components .
Don't rule our your ignition switch having a bad connection or the base connector for the DME relay in the fuse relay box .
02-20-2019, 03:07 PM
#53
have you got the 3x wire bypass fitted whilst you are testing ?
I don't understand why there is a reluctance to do this . it immediately eliminates a lot of components .
Don't rule our your ignition switch having a bad connection or the base connector for the DME relay in the fuse relay box .
I don't understand why there is a reluctance to do this . it immediately eliminates a lot of components .
Don't rule our your ignition switch having a bad connection or the base connector for the DME relay in the fuse relay box .
When it dies everything comlletely goes dead there’s no battery light oil light or even my parking brake light on the dash. Loose ground?
02-20-2019, 04:02 PM
#54
Burning Brakes
I mean... fuel is being delivered to the rail and the car builds normal fuel pressure. I’ll jumper the relay but it doesn’t really seem to be a fuel issue at all.
When it dies everything comlletely goes dead there’s no battery light oil light or even my parking brake light on the dash. Loose ground?
The 3x wire bypass doesn't just supply a permanent 12v+ supply to the fuel pump . It does all of the many jobs that are normally done by both of the relays inside the DME relay can .
If everything thing is going dead when the engine cuts out thats is a very important bit of information and really helps direct you to the problem source.
What is it that could cut power to the whole ignition and dash ? .......
I would look at your ignition switch first .
I will have to refresh my memory from my electrical schematic which will take a while but do you have a factory alarm or aftermarket immobiliser fitted to the car ?
Jacob I know that you will already have checked the battery and battery terminals but just humour me and check again by removing the terminals completely and checking the battery cables and chassis ground. If you have a jump lead you could attach one end to the negative battery terminal and the other end to somewhere on the engine or gearbox .Try starting the car This will bypass your negative battery ground wire and could show up a poor connection somewhere
02-20-2019, 04:07 PM
#55
Nope! There’s no alarm/ immobilizer. I’ll see what i can find on the ignition switch as well. I need to correct my last post.
I just jumped he car again. When it stalls I have no oil pressure light on the dash, but the battery light does come on after it stalls.
The oil pressure gauge indicates the car builds oil pressure.
I just jumped he car again. When it stalls I have no oil pressure light on the dash, but the battery light does come on after it stalls.
The oil pressure gauge indicates the car builds oil pressure.
02-20-2019, 04:36 PM
#56
Burning Brakes
mmmm just a thought , you replaced the crank position sensor and speed sensor didn't you ?
I wonder if the ECU is shutting down the engine because it isn't seeing sufficient engine speed ......
its a safety feature that prevents fire in the case of an accident . The ECU won't normally let the car start if the revs are not high enough but I suppose it is possible it could start and be shut down by the ECU. if the speed sensor is sending faulty information.
you said previously that everything went dead ?.......is that different now
I wonder if the ECU is shutting down the engine because it isn't seeing sufficient engine speed ......
its a safety feature that prevents fire in the case of an accident . The ECU won't normally let the car start if the revs are not high enough but I suppose it is possible it could start and be shut down by the ECU. if the speed sensor is sending faulty information.
you said previously that everything went dead ?.......is that different now
02-20-2019, 04:52 PM
#57
mmmm just a thought , you replaced the crank position sensor and speed sensor didn't you ?
I wonder if the ECU is shutting down the engine because it isn't seeing sufficient engine speed ......
its a safety feature that prevents fire in the case of an accident . The ECU won't normally let the car start if the revs are not high enough but I suppose it is possible it could start and be shut down by the ECU. if the speed sensor is sending faulty information.
you said previously that everything went dead ?.......is that different now
I wonder if the ECU is shutting down the engine because it isn't seeing sufficient engine speed ......
its a safety feature that prevents fire in the case of an accident . The ECU won't normally let the car start if the revs are not high enough but I suppose it is possible it could start and be shut down by the ECU. if the speed sensor is sending faulty information.
you said previously that everything went dead ?.......is that different now
That makes the most sense honestly. Without an oscilloscope I can’t properly test the signal from the speed sensor so I might need to get it to a shop.
And yes I was incorrect when I said that the dash went dead completely. Initially the first time I started the car the dash did go dead but that was because the battery was so dead as soon as the jump box stopped giving power to the battery and the car died after it was started, the battery was so low nothing on the dash was illuminating.
To eliminate the battery and jump box, I jumped the car again with another running car and allowed the battery to charge for some time. The car showed the same results only this time the proper lights on the dash were still lit. Again except for that oil pressure light.
I looked up muliple threads on 944s starting then dying immediately. It could still be a multitude of things ranging from a loose vacuum hose, to a loose ground, or bad sensors. Tonight I’ll have a buddy help me smoke test the car to get rid of any vacuum leaks and I’ll go from there. I’ll plug in my old DME and see if that changes anything.
02-20-2019, 06:44 PM
#58
Burning Brakes
you need to buy a new battery for the car. You cannot expect a battery booster to supply enough amperage to power the car when its running. Its not about volts otherwise we would be able to start the car on a torch battery. its all about amperage or amphour rating .
You are still hitting things at random .
If you have a fuel pressure gauge attached to the fuel rail....... tell me exactly what the fuel pressure is when it is running and what exactly happens to the fuel pressure the second the engine dies . That will tell me something useful and help tremendously with the diagnosis .
You are still hitting things at random .
If you have a fuel pressure gauge attached to the fuel rail....... tell me exactly what the fuel pressure is when it is running and what exactly happens to the fuel pressure the second the engine dies . That will tell me something useful and help tremendously with the diagnosis .
02-20-2019, 06:57 PM
#59
you need to buy a new battery for the car. You cannot expect a battery booster to supply enough amperage to power the car when its running. Its not about volts otherwise we would be able to start the car on a torch battery. its all about amperage or amphour rating .
You are still hitting things at random .
If you have a fuel pressure gauge attached to the fuel rail....... tell me exactly what the fuel pressure is when it is running and what exactly happens to the fuel pressure the second the engine dies . That will tell me something useful and help tremendously with the diagnosis .
You are still hitting things at random .
If you have a fuel pressure gauge attached to the fuel rail....... tell me exactly what the fuel pressure is when it is running and what exactly happens to the fuel pressure the second the engine dies . That will tell me something useful and help tremendously with the diagnosis .
When cranking it builds to this pressure. About 33psi. Stays there when the car runs and after the car stalls still reads 33 psi.
It’s been about 2.5 hours since I last started the car the pressure is at 10psi currently.
02-20-2019, 07:09 PM
#60
Burning Brakes
that is not the most accurate gauge on a car but the most important thing it is telling us is that the engine is not cutting out due to the fuel system suddenly losing fuel pressure .
Good we are getting somewhere.
We can probably assume that the injectors , the fuel pump and the non return valve are not leaking . Same goes for the FPR and damper and the fuel system generally.
Because the car is actually starting and running for a few seconds we can also assume that the DME relay the ECU , the crank position sensor , injectors , and secondary ignition system are also all working ......otherwise the car would not start and run.
So we are now looking for something that would cause one or more of those components to stop working as they should .
Good we are getting somewhere.
We can probably assume that the injectors , the fuel pump and the non return valve are not leaking . Same goes for the FPR and damper and the fuel system generally.
Because the car is actually starting and running for a few seconds we can also assume that the DME relay the ECU , the crank position sensor , injectors , and secondary ignition system are also all working ......otherwise the car would not start and run.
So we are now looking for something that would cause one or more of those components to stop working as they should .